Circulation line and side stream filter fuel system



y 1964 J. TWIBELL 3,131,751

CIRCULATION LINE AND SIDE STREAM FILTER FUEL SYSTEM Filed Sept. 23, 1959INVENTOR.

LLOYD J. TWIBELL United States Patent 3,131,751 CIRCULATION LINE ANDSIDE STREAM FILTER FUEL SYSTEM Lloyd J. Twibell, Grchard, Nebr. FiledSept. 23, 15163, Ser. No. 310,695 11 Elaine. (Cl. 158-364) Thisinvention relates to fuel systems of the type having a by-pass lineleading to a fuel tank from the carburetor area to form constantcirculation of fuel to and from the fuel tank whereby at some point insaid circulation, a circulating filter can be inserted to provide forthe continuous filtering of fuel.

As heretofore conceived such systems have had many disadvantages. Thechief among these disadvantages has been in that two filters have beenused in the circulation line heretofore, but these two filters have beenused in such a way that they are both in the circulation line, whereastheir effect is merely additive in the reducing of impurities in thecirculation line.

An example of this is to be found in the Patent #2,795,269, issued June11, 1957, to L. L. VVitte and titled: Fueling System for an InternalCombustion Engine.

In this patent, two filtering devices are provided, neither one of whichis disposed in a line leading from a circulating fuel line to acarburetor.

It is, therefore, an object of this invention to provide a fuel systemof the type described in which the carburetor protection filter isdisposed in a line leading from a fuel constant circulation line to thecarburetor, whereby the standby filter is not directly in the fuelcirculation line, to the end that the main load of filtering is carriedon by a filter in the main circulation line, so that the carburetorprotection filter becomes merely a stand-by fil er receiving through ita far lesser amount of fuel flow than the fuel flow in the circulationline, whereby the carburetor protection filter is normally relativelyclean and is likely only to become clogged when and if an operator failsto empty a main circulating fuel line filter.

It is an object of this invention to provide for flow through thecirculating fuel line to pass closely by the entrance to the fuel tankfilter pipe, whereby a motorist can look through the filter pipe andvisually determine whether there is normal flow into the fuel tank fromthe by-pass line, whereby if the fuel flow has been shut off or beenconsiderably impeded by impurities, he is warned that it is time for himto clean out his circulation line filter to replace his system in normaloperating order. It will not be necessary at such times for the operatorto bother to clean out his stand-by filter at the carburetor, however,because the main load of filtering is done in the circulating fuel linefilter because the fuel flow therethrough is constant and of a muchgreater volume than is the fuel flow through the stand-by carburetorfilter and to the engine.

A second major disadvantage of constant circulation filter-systems asdescribed has been the greater frequency of clogging that can occur ifthere are two filters to be carefully watched instead of one filter. Thehuman error involved in watching two filters increases the frequency ofthe clogging of the carburetor float valve withiron oxide or other fuelimpurities, to the end that an engine can stop running because the rustor iron oxide particles get under the float valve preventing it fromseating, and thereby causing the engine to be flooded. A still morefrequent failure of a carburetor from clogging occurs when a car willnot start because of excess flooding due to this same problem of acarburetor valve being held open by rust.

Much of the difiiculty in starting automobiles in both summer and winterhas been actually caused by rust and other impurities in fuel, the rust,coming from transportation and storage facilities, such as the storagetank at a filling station, the latter facilities normally not beingcoated to protect them against oxidation, although the fuel tank in anautomobile is normally coated.

Some motorists have thought that the filter commonly disposed in frontof a carburetor will protect the carburetor adquately. Experts have longrecognized that this is not the case.

People have long desired that it would be possible and practical toplace extra filters in the fuel line between the tank and carburetor.This has not been practical, however, because such extra filters, whenclogged, shut off fuel to the engine, whereby an automobile might stopin the midde of a desert or in the middle of a dangerous trafficcondition.

It is, therefore, an object of this invention to provide clean fuel fiowto the carburetor without impeding flow by clogged filter and achievingthis through providing the main load of filtering at a circulating fuelline filter disposed in a circulating fuel line, and preferably in aby-pass line portion of the circulating fuel line, whereby a clogging ofthe circulating fuel line filter will not interrupt fuel flow tothecarburetor, whereby upon clogging of the circulating fuel line filter, acar can continue to operate without danger of being stopped in a desertor dangerous traific condition.

A further object is to provide a motorist with absolute assurance thathis stand-by filter at his carburetor will never become clogged so longas he takes the precaution of inspecting his filler pipe to see if flowfrom his by-pass line indicates cleaning of his circulating line filter,provided he then properly cleans the circulating line filter.

A further major disadvantage of by-pass line filter systerns of theprior art has been in the presence of a spring-. loaded valve in theby-pass line forming a constriction. Such spring-loaded valves areadapted to open during operating flow of fuel. However, when the fuelpump is shut ofi', they tend to close, thereby blocking the bypass fuelline. This blocking creates a great disadvantage because of its effectin combination with the diaphragm spring of the fuel pump. Even after afuel pump has been shut off, its diaphragm spring tends to continue tocreate a pressure against fuel in the line leading to the carburetor.With my system of this invention, this pressure causes no harm becauseit is dissipated harmlessly through the open by-pass line of my system,this disipation occurring immediately as soon as the motor stops.However, in systems of the prior art, dissipation of the diaphragmspring initiated pressure on the fuel cannot be dissipated through theby-pass line because of the aforesaid spring-loaded valve which closesand clogs the by-pass line, whereby the pressure in the line leading tothe carburetor causes gasoline to be forced into the carburetor, to theend that cylinder wall lubrication becomes excessively diluted andwashed away whereby motor starting is seriously hampered and rapid wearthrough inadequate lubrication reduces motor life.

It is, therefore, an object of this invention to provide a system asdescribed with a by-pass fuel line which is constanly open so that whenit is free of impurities, or substantially free of impurities, myby-pass line maintains an amount of frictional resistance to fuel flowwhich is vastly lesser than the resistance present when a springloadedvalve is closed, whereby my constantly open bypass line freelydissipates gasoline pressure after an engine has stopped wherebycylinder wall lubrication is not diluted and washed away.

In the above objectives, I have discussed the compara tive relationshipbetween my system and other by-pass line constant recirculation of fuelsystems. Let me say that before the public marketing of my invention,there was never, to my knowledge, any by-pass line filtering system onthe market. For that reason, it has seemed to me reasonable to assumethat even though one such system has been previously described in theabove-mentioned patent to L. L. Witte, yet there never has been anywidely successful marketing of any by-pass line gasoline recirculationsystems.

As regards those fuel systems that have been widely marketed, beforepublic exposure of my invention, all of those systems have been subjectto the clogging of the carburetor float valve problems above described,vapor lock problems which I will now discuss, and excessive fuelpressure problems which my system also solves as I will describe.

Fuel systems previously widely marketed have been without any way forvapor to escape. It is an object of this invention, therefore, toprovide a by-pass line leading back to the fuel tank which gives theadvantage of the dissipation of vapors through the by-pass line to thefuel tank. As all fuel tanks have a conventional vent pipe for vapor andto admit air, the vapor escapes from the automobile harmlessly. For thisreason, I believe it is fair to say that my system has provided the mostpractical solution to vapor lock heretofore achieved.

The problem of excessive fuel pressure has long been recognized as oneof the major unsolved problems of modern carburetion. Most fuel pumpsdeliver excessive pressure. The average fuel pump of a full sizeautomobile manufactured in the United States has a pressure of from 47pounds, when new. However, when such a fuel pump is old, and long beforethe same automobile is put out of service, its fuel pump will have astretched diaphragm and its pumping pressure will, by that time, begreatly reduced even as low as two and three pounds, later even less.

For this reason, most manufacturers install fuel pumps on their newautomobiles which are of pumping capacity greatly in excess of enginerequirement, as leads to excess fuel pressure problems.

Such excess fuel pressure problems are firstly and foremost anexcessively rich gasoline mixture proportional to the air available, tothe end that fuel is wasted and power is lost. A gasoline-air explosionis similar to a bonfire in that an excess of fuel suddenly dumped onto afire without sufficient air results in a smothering of the explosion toa degree proportional to the excess of gasoline, in my opinion.

An automobile which is receiving an excessively rich fuel mixture willrun roughly. Such an automobile will not respond to accelerationproperly. It will not respond smoothly. It will even have an unpleasantsound.

Excessive fuel pressure is especially bad in an automobile that has rustand other sediment in its fuel. When even a small amount of sediment isholding a carburetor float valve open, the excess pressure can push agreat and harmful amount of gasoline through the carburetor and into theengine far beyond what is needed for suflicient carburation, wherebymaximum power is not achieved,

fuel is wasted, acceleration is sluggish, and idling is rough.

Excessively rich mixture also dilutes cylinder wall lubrication,bringing about lesser motor life.

The black smoke that comes from an exhaust pipe as a result of excessivefuel in the mixture causes increased air pollution which is the majorproblem in most urban areas and in particularly the lower west coastwhere this is a major cause of smog.

A further object of the invention is to provide a circulating fuelsystem which is adapted to preserve the life of a fuel pump to reducethe problems which ensue from the loss of pumping power as a fuel pumpbecomes worn out, this being accomplished through the provision of aby-pass line to the fuel tank for relieving pressure, whereby a fuelpump does not need to pump as hard as it pumps against the substantiallymore closed line that normally leads from fuel pump through thecarburetor. More particularly, the bypass line provides a more constantpressure at the carburetor regardless of the amount of pumping pressureinasmuch as the pressure at the carburetor can be regulated by amanually controlled valve in the by-pass line, whereby when a pump isnew and pumping strongly, the manually controlled valve can be openedmore widely which gives desired pressure at the carburetor, but whichalso by-passes a greater volume of fuel creating a lesser back pressureon the pump, thereby improving life of the fuel pump.

A further object is to provide a system as described in the use of whichthe by-pass fuel line provides sufiicient frictional resistance to fuelflow therethrough to provide in cooperation with the fuel pump asufficient operating fuel pressure against the carburetor whereby it isnot necessary to have a reservoir in the by-pass line. Such a reservoiris shown in the above-mentioned patent to Witte. By this means, Iprovide for the absence of a reservoir so that there is no substantialyquantity of gasoline to flow down from any portions of my by-pass linewhich might be disposed above the carburetor so that there is nosubstantial quantity of gasoline flowing down from the by-pass line intothe carburetor when the pump and engine have stopped, whereby themaximum preservation of lubrication in the engine and the cylinder wallsis preserved. Also, for this reason, it is an object to provide anyportions of the by-pass line which might be disposed above thecarburetor with a minimum of internal volume so that the by-pass linesthemselves do not contain a substantial quantity of gasoline to How downto the carburetor after the engine and pump have stopped.

This application is a continuation-in-part of the appli cants co-pendingpatent application Serial No. 6,707, filed February 4, 1960, titledCirculating Double Filter Fuel System, and now abandoned.

Other and further objects and advantages of the present invention willbe apparent from the following detailed description, drawings andclaims, the scope of the invention not being limited to the drawingsthemselves as the drawings are only for the purpose of illustrating away in which the principles of this invention can be applied.

Other embodiments of the invention utilizing the same or equivalentprinciples may be used and structural changes may be made as desired bythose skilled in the art without departing from the present inventionand the purview of the appended claims.

In the drawings:

The drawing shows -a longitudinal sectional view through the forwardportion of a motor vehicle with an additional filter or sedimenteliminator connected by a tube to the fuel line of the vehicle and tothe neck of the fuel tank of the vehicle by a fuel return tube having acontrol valve therein.

In the accompanying drawing, and in the following specification, thesame reference characters are used to designate the same parts andelements throughout, and in which the numeral 10 refers to the inventionin its entirety, numeral 12 indicating a second filter connected by aflexible hose 14 to a tube 16, and the tube 16 is con nected to the fuelline 18 of the engine 20 by an inverted T 22. The second filter 12 isconnected to a control valve 24 by a tube 26 and the valve 24 isconnected by a tube 28 to the neck 30 of a fuel tank 32.

The fuel line 18 extends from a fuel pump 34 and the intake of the pumpis connected by a tube 36 to the tank 32. The fuel line 18 is providedwith a first filter 38 which is conventional.

The fuel pump 34 is of a conventional type having a spring loadeddiaphragm which has a tendency to seek its normal relaxed position afterpumping has stopped, this tendency tending to force fuel through theline 18 into the carburetor and engine causing dilution of cylinder Walllubrication and washing away thereof as is a common problem with thistype of conventional fuel pump. This problem is solved by dissipation ofsuch pressure through the by-pass line of my invention back to the fueltank.

The tube 36 can also be called the post-tank first fuel line 36connecting the suction side of the fuel pump 34 with the bottom of thefuel tank 32.

The return line 28 is secured to the upper portion of the fire wall 40of the vehicle by a bracket 42 which is positioned as close to the upperend of the fire wall as possible.

With the second filter 12 positioned in the discharge line 18 of thepump 34 fuel circulated through the return line 28 is continuouslyfiltered, and as the fuel passes into the carburetor 44 it is filtered asecond time by the first filter 38. With all rust and other foreignmatter continuously filtered from the fuel, smooth easy running of theengine is assured, and greater mileage is obtained from the fuel.

The carburetor 44 has as a part of its continuity the T-fitting 22 andthe upper part of the filter 38, all of these parts, the line 18 withits T-fitting 22 and filter 38, are all together to be considered apost-pump second fuel line 60 connecting the discharge side of the fuelpump 34 with the carburetor 44.

The filter 38 can also be called a stand-by filter 38 or a stand-bycarburetor protection first fuel filter 38.

The invention further has a by-pass line 66 which includes the upperportion of the T-fitting 22 which is above the post pump line 18, thetube 16, flexible hose 14, a by-pass line or circulating second filter12, the manual control valve 24, and the tube 28. The by-pass line willbe seen to by-pass excess fuel from the post pump line 69 to fuel tank32.

It is important that the tube 16 and that portion of the Tfitting 22 towhich it is connected take off from-the post-pump line 6% in an upwarddirection to avoid vapor lock.

It will be seen that a constant circulation line generally indicated at'70 is formed by the by-pass line 66 as described, the filler pipe 36,thefuel tank 32, the post-tank line 36, the fuel pump 34, and thatportion of the postpump line 69 which extends to the center of the T-fitting 22.

The constant circulation will be seen to follow the various arrows 86,82, 84, 86, 83 and 89 in the flow involved in the constant circulationline 70.

It will be seen that the manually controlled valve 24 in the by-passline as described controls fuel pressure developed by the pump wherebythis pressure can be reduced as is normaiy desired, the valve 24 beingadapted to provide a preset orifice whereby the valve 24 permits fuelpressure at the carburetor 44 to drop to zero pounds when the engine isstopped whereby fuel is not forced into the carburetor 44 (as 'it is atthat time unwanted because of its washing away of lubricant).

It will be seen that the valve 24 is disposed on the fuel tank side inthe bypass line from the filter 12 which 6 shall be called a secondfilter 12, so that the valve 24 is protected from clogging by the secondfilter 12.

It will be seen that the by-pass line as above defined is free of anyelement between its ends which is a part of the by-pass line itself andsuch as would cause, by itself, a variance in frictional resistance tofuel flow at such element during operation by varying the effective sizeof the by-pass line. In the sentence preceding, the term by itself isused to distinguish from impurities which could clog the circulationfilter 12 causing a variance in frictional resistance to fuel flow. Toexpress this in another way and to be more specific, the by-pass line isfree in the area between its ends of any spring-loaded and controlledvalve causing a. variance in frictional resistance to fuel flow duringoperation by varying the effective size of the by-pass line.

It will be further seen that the by-pass line, as described, is free ofany element (such as a spring controlled valve) between its ends causinga fuel pressure in said system to be exerted on the carburetor 44 afterthe engine has stopped (as is then unwanted because such fuel pressureforces fuel into the cylinders and washes away lubricant from around thecylinder walls).

The filters 12 and 38 are both preferable magnetic filters ofconventional'construction as they are particularly capable of filteringout iron oxide rust particles.

Thev reason I prefer not to have a spring-controlled valve in theby-pass line is because such a valve would close by its spring pressureas soon as pumping pressure stopped. This closing would preventdissipation of unwanted pressure in the post-pump line, a dissipationharmlessly cut off into the by-pass line which is a dissipation which isa desirable feature of this invention and prevents such pressure fromgetting into the engine after the engine and pump have been turned offwhere it can there dilute and wash away cylinder wall lubricant.

It will be seen that with the circulation line 70 de scribed, the firstfuel filter 38 is not in the circulation line 70, but is, in a sense upa side stream in a portion of the post-pump line 66 which is identifiedin the drawings by the numeral and which shall be called a side streamline 90 for clarity of understanding. The vast bulk of fuel movement isin the circulation line with a fiow much greater than goes into theengine through the side stream line 90.

The net results is that the first filter 38 becomes merely a standbyfilter or we can call it a side stream filter 38, to the end that a flowin the direction of the arrow 92 through the side stream stand-by filter38 is so little in comparison with flow through the circulation filter12 that the circulation filter 12 can also be called the main filter 12.

The net result is that the stand-by filter 38 will never be clogged solong as the operator takes the precaution of sighting aiong through thefilter pipe from the line 28 to be sure that the fiow therefrom iscontinuous and provided the operator cleans out the main circulatingfuel filter 12 whenever stoppage of flow from the line 28 is visiblethrough the open end of filler pipe 30.

For purposes of definition, the lower end of the tube 23 terminatessufiiciently close to the openable right end of the filler pipe 34) asto permit visibility of flow from the tube 28.

The term filler pipe 36 can also include as much as of what might bepractically considered the other portion of tank 32 as is necessary inorder to define the lower outlet of tube 28 as being suificiently closeto the openable right end of the filler pipe 39 as to permit flow fromthe tube 28 to be seen through the filler pipe 30.

It will be seen that the circulating filter 12 could be positionedanywhere in the circulating line 70, for example, in the post-tank line36 where it would filter to good advantage, but if in the post-tank line36,, then there would be the disadvantage that clogging of filter 12when, in line 36, would stop the engine. Whereas 7 clogging of filter 12when in the by-pass line does not stop the engine and many miles can yetbe driven to safety before stand-by side stream filter 38 clogs.

From the foregoing description, it is thought to be obvious that acirculation line and side stream filter fuel system constructed inaccordance with my invention is particularly well adapted for use, byreason of the convenience and facility with which it may be assembledand operated, and it will also be obvious that my invention can bechanged and modified without departing from the principles and spiritthereof, and for this reason, I do not wish to be understood as limitingmyself to the precise arrangement and formation of the several partsherein shown in carrying out my invention in practice, except asclaimed.

I claim:

1. A fuel system for an internal combustion engine comprising: a fueltank, a fuel pump, a carburetor of the float valve controlled inputtype, a post-tank first fuel line connecting the bottom of said fueltank with the suction side of said fuel pump, a post-pump second fuelline connecting the discharge side of said pump with said carburetor, astand-by first fuel filter in said post-pump second line, by-pass fuelline connecting a top portion of said fuel tank with said post-pumpsecond fuel line on the pump side of said stand-by filter, said bypassfuel line providing, when cleaned of impurities, a sufiicient frictionalresistance to fuel flow therethrough to provide in cooperation with saidfuel pump a sufficient operating fuel pressure against said carburetor,whereby said bypass line, said fuel tank, said post-tank line, said fuelpump, and a portion of said post-pump line all together define aconstant circulation fuel line while said pump is operating, acirculating fuel filter in said circulation line, whereby saidcirculating fuel filter does the greater filtering and said stand-byfilter thereby remains more clean as said stand-by filter is not in saidcirculating fuel line.

2. The combination of claim 1 in which said fuel pump is of the typehaving a spring-loaded diaphragm and in which the said fuel pressurewhich is in said post-pump line after said pump and engine are shut offis caused by the tendency of said diaphragm spring to seek its normalrelaxed shape.

3. The combination of claim 1 in which said by-pass line, when free ofimpurities, remains open after said engine and fuel pump are shut offwhereby fuel pressure in said post-pump line is dissipated through saidby-pass line after said pump has stopped to prevent said pressure fromforcing fuel through said carburetor to prevent fuel from excessivelydiluting and washing away cylinder wall lubrication so that thepreserved lubrication can make motor starting easier and preserve motorlife.

4. The combination of claim 1 in which said by-pass line has no upperportions disposed above said carburetor and thereby providing anundesired gravity pressure against fuel flow which upper portions are ofinternal volume substantially greater than necessary for flow of bypassfuel for constant substantial volume of fuel circulation for filteringsuch circulating fuel, and also the said cooperation with said fuel pumpof said by-pass line fiow resistance for providing said sufiicientoperating pressure being provided substantially by said frictionalresistance alone and not to a substantial extent by gravity, wherebythere is no substantial quantity of gas to flow down from said by-passline into said carburetor when said pump and engine have stopped wherebysubstantial preservation of lubrication in said engine is achievedthereby.

5. A fueling system for an internal combustion engine comprising: acarburetor, a fuel pump, a fuel tank, a first line connecting said fuelpump to said fuel tank, a second line connecting the discharge side ofsaid fuel pump with said carburetor, a by-pass line connecting thesecond line to the fuel tank, a first filter in said second line anddisposed on the carburetor side of the connection between said secondand by-pass lines, a second filter in said bypass line, a manuallycontrollable valve in said by-pass line for controlling fuel pressuredeveloped by said pump, said valve being adapted to provide a pre-setorifice whereby said valve permits fuel pressure at said carburetor todrop to zero pounds when said engine is stopped whereby fuel is notforced into said carburetor as is then unwanted because of its washingaway of lubricant around the cylinder walls.

6. The combination of claim 5 in further combination with: said valvebeing disposed on the fuel tank side in said by-pass line from saidsecond filter where said valve is protected from clogging by said secondfilter.

7. A fueling system for an internal combustion engine comprising: acarburetor, a fuel pump, a fuel tank, a first line connecting said fuelpump to said fuel tank, a second line connecting the discharge side ofsaid fuel pump with said carburetor, a by-pass line connecting thesecond line to the fuel tank, a first filter in said second line anddisposed on the carburetor side of the connection between said secondand by-pass lines, a second filter in said bypass line, a manuallycontrollable valve in said by-pass line for controlling fuel pressuredeveloped by said pump, said valve being adapted to provide a pre-setorifice whereby said valve permits fuel pressure at said carburetor todrop to zero pounds when said engine is stopped whereby fuel is notforced into said carburetor as is then unwanted because of its washingaway of lubricant around the cylinder walls, said by-pass line beingfree of any element between its ends causing a fuel pressure in saidsystem to be exerted on said carburetor after said engine has stopped.

8. A fueling system has an internal combustion engine comprising: acarburetor, a fuel pump, a fuel tank, a first line connecting said fuelpump to said fuel tank, a second line connecting the discharge side ofsaid fuel pump with said carburetor, la by-pass line connecting thesecond line to the fuel tank, a first filter in said second line anddisposed on the carburetor side of the connection between said secondand bypass lines, a second filter in said bypass line, a manuallycontrollable valve in said by-pass line for controlling fuel pressuredeveloped by said pump, said valve being adapted to provide a pre-setorifice whereby said valve permits fuel pressure at said carburetor todrop to zero pounds when said engine is stopped whereby fuel is notforced into said carburetor as is then unwanted because of its washingaway of lubricant around the cylinder walls, said by-pass line beingfree between its ends of any spring loaded and controlled valve causinga variance in frictional resistance to fuel flow during operation byvarying the size of said by-pass line.

9. A fueling system for an internal combustion engine comprising: acarburetor, a fuel pump, a fuel tank, a first fuel line connecting thesuction side of said fuel pump with the bottom of said fuel tank, asecond fuel line connecting the discharge side of said fuel pump withthe carburetor, a first fuel filter in said second fuel line, a bypassfuel line connecting said second fuel line with the top of said fueltank, said by-pass connection being made on the fuel pump side of saidfirst fuel filter, a part of said by-pass line being flexible, a secondfuel filter in said by-pass fuel line, an adjustable orifice in saidby-pass fuel line, said by-pass line being free of any element betweenits ends which is a part of the by-pass line itself and which, byitself, causes a fuel pressure in said system to be exerted on saidcarburetor after said engine has stopped, these component parts beingoperatively correlated to provide increased fuel circulation byeffective sediment removal to produce multiple filtered fuel for thecarburetor, to provide adjustable fuel pressure to the carburetor whilethe motor is running and no fuel pressure while the motor is stopped, toeliminate vapor lock and to increase the removal of sediments from saidfuel tank.

10. The combination of claim 1 in which said fuel tank has aconventional filler pipe having an openable filling end and in which theoutlet end of said byqpass fuel line is connected to said filler pipesufficiently close ts its outlet end as to permit visibility of flowinto said filler pipe from said by-petss line, whereby stoppage of suchflow and need to clean out said circulating filter can quickly bedetected.

11. The combination 00S claim 1 which a portion of said by-pass line isflexible to absorb vibrations.

References (Iitefi in the file of this patent UNIT ED STATES PATENTS2,720,313 Piattison Oct. 11, 1955 2e 2,795,269 Witte June 11, 19572,818,111 Ross Dec. 31, 1957 FOREIGN PATENTS 5 445,724 Great BritainApr. 17, 1936 818,922 Great Britain Aug. 26, 1959 OTHER REFERENCESAmerican-Bosch Fuel Injection Equipment for Diesel 10 Engines (G. W.Baierlein), published by United American Bosch Corporation (Sptingfield,Mass.) 1937 (pages 19 and 30, particularly Figures 28 and 55, reliedon).

1. A FUEL SYSTEM FOR AN INTERNAL COMBUSTION ENGINE COMPRISING: A FUELTANK, A FUEL PUMP, A CARBURETOR OF THE FLOAT VALVE CONTROLLED INPUTTYPE, A POST-TANK FIRST FUEL LINE CONNECTING THE BOTTOM OF SAID FUELTANK WITH THE SUCTION SIDE OF SAID FUEL PUMP, A POST-PUMP SECOND FUELLINE CONNECTING THE DISCHARGE SIDE OF SAID PUMP WITH SAID CARBURETOR, ASTAND-BY FIRST FUEL FILTER IN SAID POST-PUMP SECOND LINE, BY-PASS FUELLINE CONNECTING A TOP PORTION OF SAID FUEL TANK WITH SAID POST-PUMPSECOND FUEL LINE ON THE PUMP SIDE OF SAID STAND-BY FILTER, SAID BYPASSFUEL LINE PROVIDING, WHEN CLEANED OF IMPURITIES, A SUFFICIENT FRICTIONALRESISTANCE TO FUEL FLOW THERETHROUGH TO PROVIDE IN COOPERATION WITH SAIDFUEL PUMP A SUFFICIENT OPERATING FUEL PRESSURE AGAINST SAID CARBURETOR,WHEREBY SAID BYPASS LINE, SAID FUEL TANK, SAID POST-TANK LINE, SAID FUELPUMP, AND A PORTION OF SAID POST-PUMP LINE ALL TOGETHER DEFINE ACONSTANT CIRCULATION FUEL LINE WHILE SAID PUMP IS OPERATING, ACIRCULATING FUEL FILTER IN SAID CIRCULATION LINE, WHEREBY SAIDCIRCULATING FUEL FILTER DOES THE GREATER FILTERING AND SAID STAND-BYFILTER THEREBY REMAINS MORE CLEAN AS SAID STAND-BY FILTER IS NOT IN SAIDCIRCULATING FUEL LINE.